Muslim rule generally. The Ottomans had the Janissaries. The Qajars in Persia had the Ghulam. The only one of the Muslim gunpowder empires not to use slave soldiers were the Mughals who were ethnically distinct anyway. Persians and some Arabs and Turks ruling over South Asians.
Good question. I assume there was a distinction between the various foreign soldiers and the ruler’s bodyguard under the Fatimids, but I can’t say for certain.
Did the Fatimids? I thought filling military positions with captured foreign slaves was really common under Arabic rule.